ar X iv : a st ro - p h / 96 01 06 4 v 1 1 2 Ja n 19 96 Non - cosmological Signal Contributions to the COBE 1 - DMR Four - Year Sky Maps

(NASA/GSFC) is responsible for the design, development, and operation of the Cosmic Background Explorer (COBE). Scientific guidance is provided by the COBE Science Working Group. GSFC is also responsible for the development of the analysis software and for the production of the mission data sets. ABSTRACT We limit the possible contributions from non-cosmological sources to the COBE-DMR four-year sky maps. The DMR data are cross-correlated with maps of rich clusters, extragalactic IRAS sources, HEAO − 1 A-2 X-ray emission and 5 GHz radio sources using a Fourier space technique. There is no evidence of significant contamination by such sources at an rms level of ∼ 8 µK (95% confidence level at 7 • resolution) in the most sensitive 53 GHz sky map. This level is consistent with previous limits set by analysis of earlier DMR data and by simple extrapolations from existing source models. We place a 95% confidence level rms limit on the Comptonization parameter averaged over the high-latitude sky of δy < 1 × 10 −6. Extragalactic sources have an insignificant effect on CMB power spectrum parameterizations determined from the DMR data. Subject headings: cosmic microwave background — diffuse radiation — intergalactic medium – 3 –